The invention relates to a membrane plate for plate filter presses, the membrane plate including a plate wall having a plate frame around its periphery which, together with the adjacent filter plates, delimits a filter chamber on both sides of the plate. On at least one side of the plate, the membrane plate is provided with a press membrane which can be charged by a pressure medium and is provided with a continuous edge bead that is fixed in a groove in the transition region between the plate frame and the plate wall and is covered on its side facing the adjacent plate by a holding frame that is fastened to the plate edge so as to be movable, within limits, in a direction perpendicular to the plane of the plate. If the filter chamber is open, the holding frame projects beyond the plane defined by the contact surface of the filter frame.
A membrane plate of the above-mentioned type is disclosed in DE-A 3,520,653 to which corresponds U.S. Pat. No. 4,749,482. Since the holding frame of the prior art membrane plate is connected with the plate frame so as to be movable in a direction perpendicular to the plate plane, the edge bead can be held loosely or only with a slight tension in the groove when the chamber is open. The material of the edge bead is thus compressed by way of the movable holding frame only if the filter plate packet is closed. The degree of deformation is here unequivocally determined by the dimension by which the holding frame projects beyond the plane defined by the contact surface of the plate frame. As soon as the chamber is opened again, the material of the edge bead is able to relax again so that, during the relatively long opening times in operation of such a plate filter press, the material of the edge bead is able to recover. Since, moreover, the holding frame also covers part of the adjacent membrane edge, a sufficient seal results for the pressure chamber disposed between the plate wall and the membrane when the filter chamber is closed, thus permitting very high pressure forces to be exerted on the membrane. If the filter chamber is closed, the filter cloth is not pressed onto the membrane material, but only on the much more resistant material of the holding frame so that here again the danger of locally excessive stresses, which may constitute the starting point for cracks, is avoided. The holding frame is fastened to the plate frame by way of resilient snap pins.